When ESPN went on the air in 1979, there was no running water for the couple of dozen employees at the Bristol headquarters, and they used port-a-johns and worked long hours fueled only by vendor carts at the construction site.

The entire operation was run from one half-finished building, about the size of a super pet store.

The fledgling network was on the air just under 24 hours a day on cable television, then barely used, or understood.

That first 20,000-square-foot building still stands, but it has been expanded several times. The structure is now just one of 18 on a campus that has grown to 123 acres and nearly a million square feet — almost the size of Westfarms mall — so large that ESPN had to add a shuttle bus for employees and visitors five years ago.

"We went from Camp ESPN to Little City ESPN," said Chuck Pagano, ESPN's chief technology officer, who ran the control room when the business began.

Finally, after 33 years, it's done.

The last of 45 land acquisitions in Bristol and Southington — all involving a mix of businesses and modest homes — was wrapped up late last year. The last holdout, the owners of a 1,200-square-foot ranch house, had seen the campus draw increasingly near and finally flank their property on three sides.

Now, the campus is the size that it is likely to remain for the next decade, perhaps longer.

While the expansion stretches back to ESPN's earliest days, it has accelerated since 2000. The construction of the 120,000-square-foot Digital Center, opened in 2004, equipped ESPN to compete in the era of HD — high definition — and provided the most modern studios for its flagship SportsCenter broadcast.

On ESPN's first broadcast on Sept. 7, 1979, SportsCenter reached about 30,000 viewers. Today, ESPN averages 115 million viewers a month.

Construction continues full-tilt at what is known as ESPN Plaza, with the building of a second digital center — the 19th building — that will be able to adapt to rapidly changing technologies. The construction is being financed partly by a $17.5 million loan under Gov. Dannel P. Malloy's "First Five" program. A portion of the loan won't have to be paid back, depending on how many workers are hired in the next decade at ESPN, which now has nearly 4,000 at the campus.

How much the new digital center and, for that matter, the overall expansion itself, is costing isn't being disclosed by ESPN, a unit of the Walt Disney Co.

But there have been some indications of the scope of the price tag. In 2000, ESPN committed to a five-year, $500 million expansion of its campus as part of an agreement with the state for a permanent, $15 million annual state tax break. ESPN said it easily met that commitment.

As heady as the expansion is, economists and others say ESPN is facing growing competition for its long dominant position in sports programming. Both NBC Sports and Fox Sports are launching aggressive moves to beef up their offerings. Multiple cable channels, the web, tablets and mobile applications for cellphones are all potential battlegrounds.

"ESPN is the 800-pound gorilla," said Fred Carstensen, director of the Connecticut Center for Economic Analysis at the University of Connecticut. "Any time you are extraordinarily successful, you have to keep thinking about how to stay ahead of the competition. ESPN has to work hard to protect its franchise."

ESPN will have to manage the convergence of the web, tablets and cellphones as well as negotiate the most favorable contracts with cable providers that carry their programming, Carstensen said.

ESPN is well positioned for the challenge, said Mike Soltys, who heads ESPN's communications.

"Through our 33 years, there has always been strong competition," Soltys said. "In the early days, there were the three broadcast networks. As cable grew, there were more sports channels. Now, there is broadcast, cable, Internet and radio. There has been increased recognition of the value of live sports."

He adds: "But the competition that comes from others is as strong as it has ever been, but we've built a strong business that has many aspects that have become very successful."

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